Zipper tape, and container with zipper tape

ABSTRACT

A zipper tape includes: a first resin portion made of a resin composition whose main polymer is polyolefin, the first resin portion including a base strip to define a pair of base strips and an engaging portion to define a pair of mutually engageable engaging portions, the engaging portion projecting from corresponding one of mutually facing faces of the base strips; and second resin portions made of a resin composition whose main polymer is polyester, the second resin portions at least covering faces of the base strips opposite the engaging portions.

TECHNICAL FIELD

The preset invention relates to a zipper tape and a container with a zipper tape.

BACKGROUND ART

In many packaging products for foods, medical products or the like, inner layers being in contact with contents are made of polyolefin resin films, whose main component is polyethylene and/or polypropylene that are excellent in safety and heat sealability. However, the polyolefin resin, through and into which aroma components are easily permeable and/or adsorptive, sometimes emit plastic smell when used as a material of the inner layers. In addition, medicinal and/or aroma components of the contents sometimes migrate into the polyolefin resin and/or are adsorbed onto the polyolefin resin, impairing the product value. In view of the above, packaging products are known in which PET (PolyEthylene Terephthalate), being resistant to cause migration and/or adsorption of the medicinal and/or aroma components of the contents, is used as the inner layers.

For instance, Patent Literature 1 discloses a bag with a zipper tape in which an inner layer is made of PET. The inner layer of the bag disclosed in Patent Literature 1 is made of a heat-sealable PET, while the zipper member is made of a mixture resin of PET and polyester elastomer blended at a specific ratio, or a mixture resin of PET, polyethylene and a compatibilizer. In this way, the zipper member is weldable to the inner layer of the bag made of PET and flexibility is given to the zipper member to enable easy opening/closing.

CITATION LIST Patent Literature(s)

Patent Literature 1 JP 6309925 B

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, when the zipper member is made of the mixture resin as disclosed in Patent Literature 1, flexibility and welding strength to PET of the zipper member, which greatly change depending on the blend ratio of the components of the mixture, are not easily balanced. More specifically, at a high ratio of PET, the flexibility of the zipper member becomes insufficient to make it difficult to open/close the zipper member. In contrast, at a low ratio of PET, the welding strength between the zipper member and the inner layer (PET) of the bag becomes insufficient. Accordingly, it is not easy to stabilize quality relating to the zipper member of the bag with the zipper tape disclosed in Patent Literature 1.

Accordingly, an object of the invention is to provide a zipper tape reliably weldable to a container body having an inner layer containing PET while keeping functionality such as stable sealability, moderate click feeling upon unsealing, and a container with a zipper tape in which the zipper tape is welded to a container body.

Means for Solving the Problems

According to an aspect of the invention, a zipper tape includes: a first resin portion made of a resin composition whose main polymer is polyolefin, the first resin portion comprising a pair of base strips and a pair of engaging portions being engageable with each other and respectively projecting from surfaces of the pair of base strips facing with each other; and a second resin portion made of a resin composition whose main polymer is polyester, the second resin portion at least covering surfaces of the pair of base strips opposite from the engaging portions.

According to the above aspect of the invention, the engaging portions of the zipper tape, which are made of the resin composition whose main polymer is polyolefin, can maintain the functionality of the zipper tape such as stable sealability and moderate click feeling upon unsealing. Further, the bonding surface, which is made of the resin composition whose main polymer is polyester, allows the zipper tape to be reliably welded with a container body having a sealant layer containing PET.

According to another aspect of the invention, a container with a zipper tape including the above zipper tape and a container body welded with the zipper tape is provided.

For instance, the zipper-tape container formed by welding the above zipper tape to the container body having a sealant layer containing PET can achieve both of the functionality of the PET layer and the functionality of the zipper tape.

As described above, according to the aspects of the invention, a zipper tape capable of being reliably welded to a container body having an inner layer containing PET while maintaining functionality of the zipper tape such as stable sealability and moderate click feeling upon unsealing can be provided, and also a container with the zipper tape welded to a container body, which thus achieves both of the functionality of the container body and the functionality of the zipper tape, can be provided.

BRIEF EXPLANATION OF DRAWINGS

FIG. 1 is a plan view of a bag with a zipper tape according to a first exemplary embodiment of the invention.

FIG. 2 is a cross sectional view of the bag with the zipper tape shown in FIG. 1, taken along II-II lines.

FIG. 3 is a cross-sectional view of a bag with a zipper tape according to a second exemplary embodiment of the invention.

FIG. 4 is a cross-sectional view of a bag with a zipper tape according to a modification of the second exemplary embodiment of the invention.

FIG. 5 is a cross-sectional view of a bag with a zipper tape according to another modification of the second exemplary embodiment of the invention.

FIG. 6 is a cross-sectional view of a bag with a zipper tape according to a third exemplary embodiment of the invention.

FIG. 7 is a cross-sectional view of a bag with a zipper tape according to a modification of the third exemplary embodiment.

FIG. 8 is a cross-sectional view of a bag with a zipper tape according to a fourth exemplary embodiment of the invention.

DESCRIPTION OF EMBODIMENT(S)

Suitable exemplary embodiments of the invention will be described in detail below with reference to the attached drawings. It should be noted that components of the same or substantially the same function(s) and structure(s) will be denoted by the same reference numerals herein and in the drawings, omitting repetition of description thereof.

It should also be noted that the term “main polymer” herein refers to a component of the largest quantity in the components of respective layers. Specifically, when the layers are made of n (n: an integer of 2 or more) polymers, the “main polymer” means a component contained at 100/n % or more, preferably at 100/n %×1.2 or more. A component being the main polymer can be determined through infrared spectroscopy, NMR, DSC or the like. It should be noted inevitable impurities are optionally contained as long as an advantage of the invention is not impaired.

First Exemplary Embodiment

FIG. 1 is a plan view of a bag with a zipper tape according to a first exemplary embodiment of the invention. FIG. 2 is a cross sectional view of the bag with the zipper tape shown in FIG. 1, taken along II-II lines. As shown in FIGS. 1 and 2, a bag with a zipper tape 1 according to the first exemplary embodiment includes a film 10 forming a bag with a first area 11A and a second area 11B, and a zipper tape 20.

For instance, the film 10 has a single layer or multiple layers of a thermoplastic resin. More specifically, the film 10 can include a layer made of LDPE (Low-Density PolyEthylene), LLDPE (Linear Low-Density PolyEthylene), or PP (PolyPropylene). PP can be HPP (polypropylene homopolymer), RPP (polypropylene random copolymer), or BPP (polypropylene block coplymer). When the film 10 has multiple layers, a top base material can be OPP (biaxially Oriented PolyPropylene), OPET (biaxially Oriented PolyEthylene Terephthalate), or ONy (biaxially Oriented Nylon). Further, the film 10 can include an inorganic material layer formed by processes of vapor deposition of aluminum, lamination of aluminum foil, or the like. In the exemplary embodiment, a sealant layer of the first area 11A and the second area 11B of the film 10, being a layer facing the zipper tape 20, is made of a resin composition whose main polymer is a heat-sealable PET (PolyEthylene Terephthalate).

It should be noted that, while the bag body having the first area 11A and the second area 11B is formed by bonding two sheets of the film 10 with each other at a bottom seal 12 and side seals 13 in this exemplary embodiment, the first area 11A and the second area 11B are formed by folding a single sheet of film 10 at a portion corresponding to one of the side seals 13 in some embodiments of the invention. Additionally or alternatively, the film 10 is optionally interfolded at a portion(s) corresponding to the bottom seal 12 and/or the side seals 13 of the example shown in FIG. 1, thereby forming a so-called gusset. In this case, the gusset is formed by the film(s) 10 or by a separate film bonded to the film(s) 10. The bag with the zipper tape 1 can also be a stand up pouch capable of standing upright on the gusset formed at a bottom thereof.

Further, while an opening 14 of the bag with the zipper tape 1 is formed by providing the bottom seal 12 and the side seals 13 and omitting a top seal in this exemplary embodiment, the top seal can be provided in addition to the bottom seal 12 and the side seals 13 and afterward a portion between the top seal and the zipper tape 20 can be cut to form the opening 14 in some embodiments. In some other embodiments, the bag body is provided without the bottom seal 12, in other words, the bag with the zipper tape 1 is not sealed at a side opposite the zipper tape 20. In this case, the bottom seal 12 is provided after putting the contents into the bag with the zipper tape 1. The invention is applicable not only to the above-described examples but also to various known bags and containers other than bags as long as the zipper tape is weldable thereto.

As shown in FIG. 2, the zipper tape 20 includes a first member 20A welded to the first area 11A of the film 10 and a second member 20B welded to the second area 11B. The first member 20A and the second member 20B respectively include a polyolefin portion 21A and a polyolefin portion 21B made of a resin composition whose main polymer is polyolefin, a bonding resin layer 22A and a bonding resin layer 22B, and a polyester portion 23A and a polyester portion 23B made of a resin composition whose main polymer is polyester. The polyolefin portions 21A, 21B respectively include base strips 211A, 211B, and engaging portions 212A, 212B respectively projecting from surfaces of the base strips 211A, 211B facing with each other. Meanwhile, the polyester portions 23A, 23B, which cover surfaces of the base strips 211A, 211B opposite from the engaging portions 212A, 212B, define bonding surfaces 231A, 231B bonded with the first area 11A and the second area 11B of the film 10, respectively. The bonding resin layers 22A, 22B are interposed between the polyolefin portions 21A, 21B and the polyester portions 23A, 23B, respectively, to bond these portions with each other. The zipper tape 20 is producible by, for instance, co-extrusion of the resin materials of the portions.

Herein, the bonding resin layers 22A, 22B are made of, for instance, bonding resin material(s) such as polyethylene, acid-modified polyolefin, epoxy-group-containing-monomer-ethylene copolymer, copolymer of ethylene-(meth)acrylic ester and dicarboxylic anhydride monomer, ethylene-vinyl-acetate copolymer, ethylene-isobutyl acrylate copolymer, polyamide resin, thermoplastic polyester, polyvinyl acetate and copolymer thereof, styrene bonding resin, polyester bonding resin, and olefin elastomer bonding resin. Interlaminar bonding strength between the polyolefin portions 21A, 21B and the polyester portions 23A, 23B can be increased with the use of these bonding resin(s). Thus, decrease in aroma retaining property of the bag with the zipper tape 1, which is caused by pinholes created in a gap between the layers of the zipper tape 20 at the side seals 13 during or after the production of the bag with the zipper tape 1 as shown in FIG. 1, can be prevented.

In the zipper tape 20 described above, engaging portions 212A, 212B formed by the polyolefin portions 21A, 21B are engageable with each other. As exemplarily shown in FIG. 2, the engaging portion 212A having a male type cross section and the engaging portion 212B having a female type cross section are engaged with each other to close the zipper tape 20 and seal the opening 14 of the bag with the zipper tape 1. It should be noted that the engaging portions 212A, 212B are not necessarily configured in the male and female shapes. Various known shapes of the engaging portion of the zipper tape such as a combination of nail-shaped member(s), hook-shaped member(s), and/or block-shaped member(s) are applicable to the engaging portions 212A, 212B of the above example. Two or more pairs of the engaging portions are optionally provided in the polyolefin portions. In either case, the engaging portions 212A, 212B form deformed profiles projecting from the base strips 211A, 211B having substantially rectangular cross sections. It is advantageous to form the engaging portions 212A, 212B in the polyolefin portions 21A, 21B whose main polymer is polyolefin since the deformed profile as described above can be maintained to seal the opening 14 reliably when the engaging portions 212A, 212B are engaged with each other and moderate click feeling upon unsealing can be obtained when the engaging portions 212A, 212B are disengaged.

On the other hand, as in the present exemplary embodiment, when the sealant layer of each of the first area 11A and the second area 11B of the film 10 is made of the resin composition whose main polymer is heat-sealable PET, direct welding of the polyolefin portions 21A, 21B forming the engaging portions 212A, 212B and the first area 11A and the second area 11B can be difficult due to low weldability between polyolefin and heat-sealable PET. Accordingly, in the present exemplary embodiment, the surfaces of the polyolefin portions 21A, 21B opposite from the engaging portions 212A, 212B are covered with the polyester portions 23A, 23B and the bonding surfaces 231A, 231B formed on the polyester portions 23A, 23B are welded with the first area 11A and the second area 11B of the film 10, respectively. The polyester portions 23A, 23B can be stably welded on the first area 11A and the second area 11B due to the high weldability between polyester and heat-sealable PET. The polyolefin portions 21A, 21B and the polyester portions 23A, 23B can be bonded in any manner. In the exemplary embodiment, the polyolefin portions 21A, 21B and the polyester portions 23A, 23B are bonded via the bonding resin layers 22A, 22B.

According to the above-described first exemplary embodiment of the invention, the engaging portions 212A, 212B of the zipper tape 20 being made of the resin composition whose main polymer is polyolefin allow to maintain the functionality of the zipper tape such as stable sealability and moderate click feeling upon unsealing. Further, the bonding surfaces 231A, 231B being made of the resin composition whose main polymer is polyester allow the zipper tape 20 to be reliably welded with the first area 11A and the second area 11B of the film 10 whose sealant layer contains PET.

Second Exemplary Embodiment

FIG. 3 is a cross-sectional view of a bag with a zipper tape according to a second exemplary embodiment of the invention. As shown in FIG. 3, a bag with a zipper tape 2 according to the second exemplary embodiment includes the film 10 and a zipper tape 40. It should be noted that the description of the film 10, which is configured in the similar manner as in the first exemplary embodiment described above, will not be repeated hereinbelow.

As shown in FIG. 3, the zipper tape 40 includes a first member 40A welded to the first area 11A of the film 10 and a second member 40B welded to the second area 11B. The first member 40A and the second member 40B include a polyolefin portion 21A and a polyolefin portion 21B, a bonding resin layer 42A and a bonding resin layer 42B, and a polyester portion 43A and a polyester portion 43B, respectively. It should be noted that the description of the base strips 211A, 211B and the engaging portions 212A, 212B of the polyolefin portions 21A, 21B, which are similar to those in the first exemplary embodiment described above, will not be repeated hereinbelow.

The polyester portions 43A, 43B are made of the resin composition whose main polymer is polyester as in the first exemplary embodiment and cover surfaces of the base strips 211A, 211B opposite from the engaging portions 212A, 212B to define the bonding surfaces 231A, 231B. The polyester portions 43A, 43B of the exemplary embodiment respectively include rising portions 432A, 432B that cover end surfaces 213A, 213B of the base strips 211A, 211B in a width direction (top-bottom direction in FIG. 3) of the zipper tape 40. The rising portions 432A, 432B are defined in the cross sections of the polyester parts 43A, 43B by portions rising up at the ends of the width direction. The rising portions 432A, 432B can partially cover the end surfaces 213A, 213B while the rising portions 432A, 432B entirely cover the end surfaces 213A, 213B in the illustrated example. Specifically, the rising portions 432A, 432B can cover a portion of the end surfaces 213A, 213B near the polyester parts 43A, 43B respectively.

The bonding resin layers 42A, 42B are made of, for instance, bonding resin material(s) such as polyethylene, acid-modified polyolefin, epoxy-group-containing-monomer-ethylene copolymer, copolymer of ethylene-(meth)acrylic ester and dicarboxylic anhydride monomer, ethylene-vinyl-acetate copolymer, ethylene-isobutyl acrylate copolymer, polyamide resin, thermoplastic polyester, polyvinyl acetate and copolymer thereof, styrene bonding resin, polyester bonding resin, and olefin elastomer bonding resin as in the first exemplary embodiment. Further, the bonding resin layers 42A, 42B are provided not only on the surfaces of the base strips 211A, 211B opposite from the engaging portions 212A, 212B but also over the end surfaces 213A, 213B to be interposed between the polyester portions 43A, 43B and the end surfaces 213A, 213B.

In the exemplary embodiment, the similar advantageous effects as those in the first exemplary embodiment described above. Further, pinholes are eliminated in the side seals 13 (see FIG. 1), where the first member 40A and the second member 40B of the zipper tape 40 are bonded with each other on the first area 11A and the second area 11B of the film 10 since the polyester portions 43A, 43B cover the end surfaces 213A, 213B of the base strips 211A, 211B in the width direction.

More specifically, for instance, during the process providing the side seals 13 by welding the polyolefin resin of the polyolefin portions 21A, 21B can be melted to cause the end surfaces 213A, 213B of the base strips 211A, 211B to extend beyond the polyester portions to bring the polyolefin resin into contact with the resin of the sealant layer of the first area 11A or the second area 11B, where the polyolefin resin is not welded to the sealant layer, thereby possibly forming the pinholes. In the exemplary embodiment, the end surfaces 213A, 213B of the base strips 211A, 211B are respectively covered with the rising portions 432A, 432B of the polyester portions 43A, 43B to keep the resin of the polyolefin portions 21A, 21B and the resin of the sealant layer of the first area 11A and/or the second area 11B from being contacted, thereby preventing formation of pinholes. It should be noted that the similar effect can be achieved when portions being capable of covering the end surfaces of the base strips 211A, 211B are formed in the polyester portions 43A, 43B even if the portions are not necessarily called the rising portions 432A, 432B.

FIG. 4 is a cross-sectional view of a bag with a zipper tape according to a modification of the second exemplary embodiment of the invention. The zipper tape 40 of a bag with a zipper tape 2A shown in FIG. 4, whose width is substantially similar to the example shown in FIG. 3, has narrower base strips 411A, 411B of the polyolefin portions 41A, 41B. The widths of the base strips 411A, 411B are, for instance, substantially the same as the widths of the engaging portions 212A, 212B as in the illustrated example, or narrower than those in the example. As a result, in the illustrated example, the polyester portions 43A, 43B form slab portions 433A, 433B that extend outward in the width direction with respect to the end surfaces 213A, 213B of the base strips 411A, 411B.

It should be noted that the slab portions 433A, 433B, which cover the end surfaces 213A, 213B of the base strip 411A, 411B in the illustrated example, can cover only a portion of the end surfaces 213A, 213B in some other embodiments. Specifically, the slab portions 433A, 433B can cover a portion of the end surfaces 213A, 213B near the polyester portions 43A, 43B. Alternatively, the slab portions 433A, 433B do not cover the end surfaces 213A, 213B in some other embodiments. In this case, inner surfaces of the first member 40A and the second member 40B of the zipper tape 40 are facing each other and each provided with step(s) between the base strips 411A, 411B and the slab portions 433A, 433B.

FIG. 5 is a cross-sectional view of a bag with a zipper tape according to another modification of the second exemplary embodiment of the invention. The zipper tape 40 of a bag with a zipper tape 2B shown in FIG. 5 has two pairs of polyolefin portions, namely, the polyolefin portions 41A, 41B and polyolefin portions 44A, 44B, each made of a resin composition whose main polymer is polyolefin. The polyolefin portions 44A, 44B, which have the same configurations as those of the polyolefin portions 41A, 41B, include narrow base strips 441A, 441B and engaging portions 442A, 442B configured in the similar manner as the above-described engaging portions 212A, 212B. In the illustrated example, the polyolefin portions 41A, 41B and the polyolefin portions 44A, 44B are juxtaposed in the width direction of the zipper tape 40 to form a so-called double zipper.

In the illustrated example, since the base strips 411A, 411B, 441A, 441B of the polyolefin portions 41A, 41B, 44A, 44B are narrow, the polyester portions 43A, 43B includes slab portions 434A, 434B respectively in between the base strip 411A and the base strip 441A and between the base strip 411B and the base strip 441B in addition to the slab portions 433A, 433B at both ends in the width direction of the zipper tape 40 as in the example shown in FIG. 4. It should be noted that the slab portions (the slab portions 433A, 433B and the slab portions 434A, 434B) herein refer to portions where the polyester portions 43A, 43B are not bonded to the polyolefin portions with regard to a thickness direction of the zipper tape 40 and the zipper tape 40 is formed by polyester portions 43A, 43B in a form of slab (board).

In the examples as illustrated in FIGS. 4 and 5, bonding areas between the polyolefin portions 41A, 41B, 44A, 44B and the polyester portions 43A, 43B are minimized by the narrow base strips of the polyolefin portions 41A, 41B, 44A, 44B and the slab portions 433A, 433B, 434A, 434B, which are provided by the polyester portions 43A, 43B on both ends in the width direction of the zipper tape 40 and at the portions between the plurality of polyolefin portions arranged in parallel with each other in the width direction, thereby restraining the zipper tape 40 from being deformed due to warpage or the like caused at the bonded portions.

It should be noted that the double-zipper configuration described above with reference to FIG. 5 is applicable to other embodiments. For instance, in the example shown in FIG. 4, two engaging portions 212A, 212B can be projected from each of surfaces of the base strips 411A, 411B facing with each other to form the double zipper. Further, in the example shown in FIGS. 2 and 3, two pairs of engaging portions 212A, 212B can be projected from each of the surfaces of the base strips 211A, 211B facing with each other to form the double zipper. The double zipper can also be formed in the other exemplary embodiment(s) and modification(s) described below by providing two pairs of engaging portions projecting from each of the surfaces of the base strips facing with each other. Alternatively, three or more pairs of engaging portions can project from each of the surfaces of the base strips facing with each other.

Third Exemplary Embodiment

FIG. 6 is a cross-sectional view of a bag with a zipper tape according to a third exemplary embodiment of the invention. As shown in FIG. 6, a bag with a zipper tape 3 according to the third exemplary embodiment includes the film 10 and a zipper tape 60. It should be noted that the description of the film 10, which is configured in the similar manner as the first exemplary embodiment described above, will not be repeated hereinbelow.

As shown in FIG. 6, the zipper tape 60 includes a first member 60A welded to the first area 11A of the film 10 and a second member 60B welded to the second area 11B. The first member 60A and the second member 60B include a polyolefin portion 61A and a polyolefin portion 61B, a bonding resin layer 62A and a bonding resin layer 62B, and a polyester portion 63A and a polyester portion 63B, respectively.

The polyolefin portions 61A, 61B, which are made of the resin composition whose main polymer is polyolefin as in the first exemplary embodiment, respectively include base strips 611A, 611B, and the engaging portions 212A, 212B projecting from mutually opposing surfaces of the base strips 611A, 611B. It should be noted that the description of the engaging portions 212A, 212B, which are configured in the similar manner as the first exemplary embodiment described above, will not be repeated hereinbelow. As in the first exemplary embodiment, the base strips 611A, 611B are provided with a surface provided with the engaging portions 212A, 212B, respectively, and a surface opposite the engaging portions 212A, 212B. In addition, the base strips 611A, 611B of the present exemplary embodiment respectively include step portions 614A, 614B at both ends in the width direction (top-bottom direction in FIG. 6) of the zipper tape 60, the step portions 614A, 614B being formed correspondingly to foldback portions 633A, 633B of the polyester portions 43A, 43B described below. In the exemplary embodiment, the step portions 614A, 614B form portions of the surfaces of the base strips 611A, 611B on which the engaging portions 212A, 212B are provided.

The polyester portions 63A, 63B, which are made of the resin composition whose main polymer is polyester as in the second exemplary embodiment, cover the surfaces of the base strips 611A, 611B opposite from the engaging portions 212A, 212B to form the bonding surfaces 231A, 231B, respectively. Further, the polyester portions 63A, 63B respectively include rising portions 432A, 432B that cover the end surfaces 213A, 213B of the base strips 611A, 611B in the width direction of the zipper tape 60. Yet further, the polyester portions 63A, 63B of the exemplary embodiment include the foldback portions 633A, 633B that cover the step portions 614A, 614B of the base strips 611A, 611B. The foldback portions 633A, 633B is defined in the cross sections of the polyester portions 63A, 63B by the end portions of the rising portions 432A, 432B rising up at the ends of the width direction, the end portions further folded back inwardly. As described above, in the exemplary embodiment, the step portions 614A, 614B form portions of the surfaces of the base strips 611A, 611B on which the engaging portions 212A, 212B are provided. Accordingly, the foldback portions 633A, 633B partially cover the respective surfaces of the base strips 611A, 611B on which the engaging portions 212A, 212B are provided. It should be noted that the base strips can have substantially rectangular cross section to form flat surfaces without the step portion in some embodiments, and the foldback portions 633A, 633B partially can cover the flat surfaces of the base strips on which the engaging portions are provided.

The bonding resin layers 62A, 62B are made of, for instance, bonding resin material(s) such as polyethylene, acid-modified polyolefin, epoxy-group-containing-monomer-ethylene copolymer, copolymer of ethylene-(meth)acrylic ester and dicarboxylic anhydride monomer, ethylene-vinyl-acetate copolymer, ethylene-isobutyl acrylate copolymer, polyamide resin, thermoplastic polyester, polyvinyl acetate and copolymer thereof, styrene bonding resin, polyester bonding resin, and olefin elastomer bonding resin as in the first exemplary embodiment. Further, the bonding resin layers 62A, 62B are provided not only on the surfaces of the base strips 611A, 611B opposite from the engaging portions 212A, 212B but also over the end surfaces 213A, 213B and the step portions 614A, 614B to be interposed between the polyester portions 63A, 63B and the end surfaces 213A, 213B and the step portions 614A, 614B.

In the exemplary embodiment, in addition to the similar advantageous effects as those in the second exemplary embodiment described above, formation of pinholes is more reliably prevented in the side seals 13 (see FIG. 1), where the first member 60A and the second member 60B of the zipper tape 60 are bonded with each other on the first area 11A and the second area 11B of the film 10 since the polyester portions 63A, 63B partially cover the surfaces of the base strips 611A, 611B on which the engaging portions 212A, 212B are provided in addition to the end surfaces 213A, 213B of the base strips 611A, 611B in the width direction. More specifically, for instance, during the process providing the side seals 13 by welding the polyolefin resin of the polyolefin portions 61A, 61B can be melted to flow beyond the rising portions 423A, 432B to bring the polyolefin resin into contact with the resin of the sealant layer of the first area 11A or the second area 11B. In this case, pinholes are possibly formed due to low weldability of the polyolefin resin with the resin of the sealant layer. In the present exemplary embodiment, the foldback portions 633A, 633B of the polyester portions 63A, 63B, which additionally cover the surfaces of the base strips 611A, 611B on which the engaging portions 212A, 212B are provided, prevent the resin of the polyolefin portions 61A, 61B from contacting the resin of the sealant layer of the first area 11A or the second area 11B, thereby more reliably preventing the pinholes from being formed. It should be noted that the similar effect can be achieved when portions being capable of partially covering the surfaces of the base strips 211A, 211B on which the engaging portions 212A, 212B are provided is formed in the polyester portions 63A, 63B even if the portions are not necessarily called the foldback portions 633A, 633B.

Modifications

FIG. 7 is a cross-sectional view of a bag with a zipper tape according to a modification of the third exemplary embodiment. In a bag with a zipper tape 3A shown in FIG. 7, the foldback portions 633A, 633B of the polyester portions 63A, 63B are extended to reach the roots of the engaging portions 212A, 212B, respectively. Even in this case, the polyester portions 63A, 63B partially cover the surfaces of the base strips 211A, 211B on which the engaging portions 212A, 212B are provided as in the example described above with reference to FIG. 6 since the roots of the engaging portions 212A, 212B are not covered with the foldback portions 633A, 633B. It should however be noted that the step portions 614A, 614B are not provided in the example shown in FIG. 7.

In the second and third exemplary embodiments, the pinholes can be prevented from being formed upon providing the side seals 13 in the bag with the zipper tapes 2, 3. The bag with the zipper tape having the inner layer of the film 10 made of a resin composition containing PET exhibits excellent aroma retaining property, which can be enhanced by eliminating the pinholes. It should be noted that, even without the configuration for eliminating the pinholes as in the first exemplary embodiment, it is possible not to form prominent pinholes depending on the material and/or dimension of the polyolefin portions 21A, 21B. Otherwise, some pinholes can be acceptable depending on the performance required for the bag with the zipper tape 1. For the similar reasons, the configuration of the second and third exemplary embodiments can be designed as desired depending on the necessity and degree for eliminating the pinholes.

FIG. 8 is a cross-sectional view of a bag with a zipper tape according to a fourth exemplary embodiment of the invention. A bag with a zipper tape 4 shown in FIG. 8 includes a zipper tape 70 including first members 70A, 70B and polyolefin portions 71A, 71B, where engaging portions of the polyolefin portions 71A, 71B define a hermetic sealing engagement including a male member 712A and a female member 712B contacting in surface with each other. An example of the hermetic sealing engagement is disclosed in, for instance, JP H08-268445 A. In the exemplary embodiment, the hermetic sealing interlock engagement by the male member 712A and the female member 712B of the zipper tape 70 enhances sealing performance and pressure resistance of the bag with the zipper tape 4. It should be noted that the polyolefin portions 71A, 71B in the example shown in FIG. 8, which include the similar narrow base strips 411A, 411B as those in the examples described above with reference to FIGS. 4 and 5, optionally include a combination of non-narrow base strip(s) and the hermetic sealing engagement as in the example described with reference to other drawings.

EXAMPLES

The heat sealability of the zipper tapes 20, 40, 60 on the sealant layer made of the resin composition whose main polymer was heat-sealable PET, and presence of pinholes in the side seals 13 of the bags with the zipper tapes 1, 2, 3 were evaluated in Example 1 (the bag with the zipper tape 1 of the first exemplary embodiment of the invention described above with reference to FIG. 2), Example 2 (the bag with the zipper tape 2 of the second exemplary embodiment described above with reference to FIG. 3), and Example 3 (the bag with the zipper tape 3 of the third exemplary embodiment described above with reference to FIG. 6).

The zipper tapes 20, 40, 60 of Examples 1 to 3 included the polyolefin portions 21A, 21B, 61A, 61B made of linear low-density polyethylene whose density was 915 kg/m³ and melt flow rate was 4.0 g/min, bonding resin layers 22A, 22B, 42A, 42B, 62A, 62B made of an bonding resin in a form of a mixture of low-density polyethylene, ethylene-propylene rubber, and alicyclic resin at a ratio of 63:23:14 (unit: wt %), and polyester portions 23A, 23B, 43A, 43B, 63A, 63B made of crystalline polyester (6:4 mixture of Vylon SI-173 and GM-913, manufactured by TOYOBO CO., LTD.). The material compositions were extruded through an extruder and were subsequently water cooled to prepare the zipper tapes 20, 40, 60.

As Comparative, a zipper tape, which had no polyester portions 23A, 23B but had the polyolefin portions 21A, 21B and the bonding resin layers 22A, 22B, was prepared using the same material compositions and through the same molding process as those for the zipper tape 20 of the first exemplary embodiment and was bonded to the same film 10 as that in the first exemplary embodiment to prepare a bag with a zipper tape.

Evaluation results of the heat sealability and the presence of the pinholes in Examples 1 to 3 and Comparative are shown in Table 1. The details of the evaluation test are as follows.

(1) Heat Sealability

The zipper tapes of Examples 1 to 3 and Comparative were welded to a laminate film (PET #12/heat-sealable PET #20 (total thickness: 32 μm)) using a heat gradient tester (manufactured by Toyo Seiki Seisaku-sho, Ltd.) at a sealing time of 1.0 second, sealing pressure of 2.0 MPa and sealing temperature of 180 degrees C. to prepare evaluation samples. Using a digital force gauge (manufactured by IMADA Co., Ltd.), heat-sealing strength (N/15 mm) between the zipper tape and the laminate film of the evaluation samples per 15 mm width was measured. It should be noted that the tensile speed at the time of sealing strength measurement was 300 mm/min. In Table 1, instance(s) showing heat-sealing strength of 15 (N/15 mm) or more are labeled as OK, and instance(s) showing heat-sealing strength of less than 15 (N/15 mm) are labeled NG.

(2) Presence of Pinholes

Alcohol colored with an ink was hermetically enclosed in the bags with the zipper tapes of Examples 1 to 3 and Comparative to evaluate the presence of pinholes at the side seals 13. In Table 1, instance(s) without leakage of the colored alcohol from the side seals are labeled OK, and instance(s) showing leakage of the colored alcohol through the side seals is labeled NG.

TABLE 1 Evaluation Results of Examples and Comparative Heat-Sealability Presence of Pinholes Example 1 OK NG Example 2 OK OK Example 3 OK OK Comparative NG NG

It was shown by the above Examples and Comparative that the zipper tapes of the exemplary embodiments of the invention exhibit improved heat sealability to a sealant layer made of a resin composition whose main polymer is heat-sealable PET. The pinholes at the side seals are less improved in Example 1 than in Examples 2 and 3. However, as described above, Example 1 is applicable depending on the necessity of preventing the formation of the pinholes and the required degree of the pinholes.

Suitable exemplary embodiments of the invention have been detailed above with reference to the attached drawings. However, the scope of the invention is not limited by these exemplary embodiments. It would be obvious for those skilled in the art to which the invention pertains that various modifications and revisions are conceivable within the technical idea described within claims, and it is understood that such modifications and revisions are naturally within the technical scope of the invention.

EXPLANATION OF CODES

-   -   1, 2, 3 . . . bag with zipper tape, 10 . . . film, 11A . . .         first area, 11B . . . second area, 12 . . . bottom seal, 13 . .         . side seal, 14 . . . opening, 20, 40, 60 . . . zipper tape,         20A, 40A, 60A . . . first member, 20B, 40B, 60B . . . second         member, 21A, 21B, 61A, 61B . . . polyolefin portion, 211A, 211B,         611A, 611B . . . base strip, 212A, 212B . . . engaging portion,         22A, 22B, 42A, 42B, 62A, 62B . . . bonding resin layer, 23A,         23B, 43A, 43B, 63A, 63B . . . polyester portion, 231A, 231B . .         . bonding surface. 

1. A zipper tape comprising: a first resin portion made of a resin composition whose main polymer is polyolefin, the first resin portion comprising a pair of base strips and a pair of engaging portions being engageable with each other and respectively projecting from surfaces of the pair of base strips facing with each other; and a second resin portion made of a resin composition whose main polymer is polyester, the second resin portion at least covering surfaces of the pair of base strips opposite from the engaging portions.
 2. The zipper tape according to claim 1, further comprising a bonding resin layer provided between the first resin portion and the second resin portion.
 3. The zipper tape according to claim 1 or 2, wherein the second resin portion at least partially covers an end surface of at least one of the base strips in a width direction of the zipper tape.
 4. The zipper tape according to claim 3, wherein the second resin portion further covers a portion of the surfaces of the base strips provided with the engaging portions, the portion being continuous with the end surface of the at least one of the base strips in the width direction of the zipper tape.
 5. The zipper tape according to any one of claims 1 to 4, wherein the second resin portion forms a slab portion extending outwardly in the width direction of the zipper tape with respect to the end surface of the at least one of the base strips.
 6. The zipper tape according to any one of claims 1 to 5, wherein the first resin portion comprises a plurality of resin portions arranged in parallel with each other in the width direction of the zipper tape, and the second resin portion forms the slab portion between the plurality of resin portions.
 7. The zipper tape according to any one of claims 1 to 6, wherein the engaging portions comprise a male member and a female member contacting in surface with each other to form a hermetic sealing engagement.
 8. A container with a zipper tape comprising: a zipper tape according to any one of claims 1 to 7; and a container body welded with the zipper tape.
 9. The container with the zipper tape according to claim 8, wherein a layer of the container body facing with the zipper tape is made of a resin composition whose main polymer is heat-sealable PET.
 10. The container with the zipper tape according to claim 8 or 9, wherein the container body forms a bag body. 